Board Stacking and Footprint Fit
The 20021311-00020T4LF: This 20-position, dual-row receptacle uses a 0.050" (1.27mm) pitch on both the mating interface and the row spacing, so the board footprint occupies a compact 10-position-per-row layout.
The mating interface carries 10.0µinch (0.25µm) gold over phosphor bronze, which supports repeated mate/unmate cycles in field-service or test applications without the fretting corrosion you'd see on tin. The post finish is 100.0µinch (2.54µm) tin, a standard solderable surface for the through-hole joint.